1. Field of the Invention
The present invention relates to a tire pressure monitoring apparatus and, more particularly, to a magnetically controlled tire pressure monitoring apparatus.
2. Description of Related Art
Generally, it is necessary to maintain sufficient tire pressure for a tire to ensure the driving safety. A tire pressure monitoring apparatus is used to detect the tire pressure and send out a warning when the tire pressure is insufficient.
Tire pressure monitoring apparatuses can be classified into external tire pressure monitoring apparatuses and internal tire pressure monitoring apparatuses. An external tire pressure monitoring apparatus is set on a valve out of a tire, and can be installed or removed at any time. An internal tire pressure monitoring apparatus is set in the tire and thus hard to be lost, and the tire can have a clean appearance. Generally; the tire pressure monitoring apparatus outputs data wirelessly.
Conventionally, a wireless tire pressure monitoring apparatus is configured to transmit electromagnetic signals periodically to output data. It transmits signals once in one time interval. However, the prior art wireless tire pressure monitoring apparatus is not convenient, since the car driver or user may want to know the tire pressure value earlier; or, during parking time, it is unnecessary to know the tire pressure value, and the wireless tire pressure monitoring apparatus does not have to transmit signals either. Therefore, the prior art wireless tire pressure monitoring apparatus still needs to be improved.